1. Technical Field
The present invention relates to a vehicle headlamp adapted to superimpose a lane marker irradiation light distribution pattern over a light distribution pattern.
2. Related Art
In the past, there has been known a vehicle lamp including a lamp unit that is adapted to selectively form a low-beam light distribution pattern or a high-beam light distribution pattern as a light distribution pattern for a headlamp.
JP-A-2003-59317 discloses a vehicle lamp that includes an additional lamp unit in addition to a main lamp unit for forming a light distribution pattern for a headlamp. The additional lamp unit forms an additional light distribution pattern that enhances the brightness of a distant road shoulder portion of the light distribution pattern.
Meanwhile, JP-A-2009-126444 discloses a vehicle lamp that includes an additional lamp unit in addition to a main lamp unit for forming a light distribution pattern for a headlamp. The additional lamp unit forms an additional light distribution pattern that enhances the brightness of a peripheral region of a vehicle visually recognized in the peripheral view of a driver. Also, JP-A-2009-126444 discloses that it is advantageous to irradiate a distant region in front of a vehicle with light including more short-wavelength components than the short-wavelength components of the light irradiating the peripheral region of a vehicle.
The vehicle lamp disclosed in JP-A-2003-59317 can irradiate a lane marker (that is, a white road surface line) on the road surface in front of a vehicle with the additional light distribution pattern that is formed by the additional lamp unit.
However, in the vehicle lamp disclosed in JP-A-2003-59317, a light source of the main lamp unit is a halogen bulb and a light source of the additional lamp unit is a halogen bulb. Accordingly, there is a problem in that the visibility of the lane marker is merely improved by the increase of the amount of light even though an additional light distribution pattern for irradiating the lane marker is superimposed on the light distribution pattern for a headlamp.
Meanwhile, the vehicle lamp disclosed in JP-A-2009-126444 can also irradiate a lane marker on the road surface in front of a vehicle with the additional light distribution pattern that is formed by the additional lamp unit.
However, in the vehicle lamp disclosed in JP-A-2009-126444, both of the normal light distribution pattern and the additional light distribution pattern are formed by the same kind of light or the normal light distribution pattern for the headlamp is formed by light including more short-wavelength components than the short-wavelength components of the additional light distribution pattern. Accordingly, there is a problem in that it is not possible to improve the visibility of the lane marker.